Luminescence studies of the rare earth ions-doped CaF2 and MgF2 films for wavelength conversion

The rare earth (RE) Eu, Yb ions-doped CaF2 and MgF2 films were prepared by the vacuum deposition and sol-gel methods. In the sol-gel method, the trifluoroacetic acid (TFA, CF3COOH) was used as a source of fluorine. The RE doped CaF2 and MgF2 films were characterized by photoluminescence (PL), photoluminescence excitation (PLE), the X-ray diffraction (XRD) and the atomic force microscopy (AFM) measurements. By the vacuum deposition, the strong luminescence due to the electric dipole allowed 4f(n)-4f(n)-(1)5d(1) transitions of Eu2+ and Yb2+ ions were observed similar with those of the crystalline bulks. The AFM surface images of sol-gel films revealed the formation of the nano-particles for alkaline earth fluorides. (c) 2005 Elsevier B.V. All rights reserved.